DE 10 2011 054 031 A1 has disclosed a device for observing and illuminating an object field on a patient from a location away from the body of the patient, comprising an optical system for observing the object field and an illumination apparatus for illuminating the object field. The device furthermore comprises a shaft, at the distal end of which a head part is arranged, which head part is widened compared to the shaft and in which at least one emitting illumination unit for homogeneous illumination of the object field is arranged. Feed lines for the at least one illumination unit extend through the shaft. Furthermore, the elongate shaft can hold an image forwarding apparatus, which forwards the image of the operation field to a proximal end of the shaft. Such a device is also referred to as “exoscope”. Exoscopes of the aforementioned type, going by the name of VITOM®, are offered by KARL STORZ GmbH & Co. KG.
In particular, such an exoscope enables the illumination and observation of an operation field during a surgical operation from a working distance of e.g. 20 to 75 cm such that the work space of the surgeon remains practically unrestricted by the exoscope. The relatively thin shaft holds the lines to the head part such that there is no need for exposed lines, which could hinder the surgeon. Connecting a video camera allows the image of the object field to be depicted on a screen, and so the latter can be observed by the surgeon without tiring; furthermore, this renders it possible for the object field to be observed by more people and for the image to be recorded, for example for documentation purposes.
The exoscope can be held by a holder having a hinged arm, at the distal end of which a gripper embodied for securely holding the exoscope, for example for gripping and damping the shaft, is arranged. By adjusting the holder it is possible to secure the exoscope at a suitable distance from the object field and in a suitable position and with suitable alignment, depending on the requirements, if the optical system of the exoscope is embodied as a side-viewing optical system with a direction of view that makes an angle of approximately 90° with the longitudinal axis of the shaft, the exoscope can be positioned, in particular, over the object field with a perpendicularly downwardly directed direction of view for observing a horizontally arranged object field, which may, for instance, be an operation field in the case of a surgical operation on the human body. By adjusting the holder, the exoscope can be brought into different positions while keeping approximately the same direction of view and, for this purpose, be swiveled about a vertical axis, depending on requirements and depending on the side from which unhindered access to the operation field is required.
In the known exoscope, the optical system is embodied as a monocular optical system, as a result of which only a restricted spatial perception of the object field is possible. However, a spatial perception of the object field may help the surgeon when performing a surgical operation. What is known from other fields of application, such as endoscopy, is that an improved spatial perception of the object field is possible using a stereoscopic optical system, in which two images of the object field are recorded from slightly different perspectives. The two images which, together, make up the stereoscopic image are also referred to as “half images”. Two observation strands are required for recording the two half images, said observation strands, in particular, respectively comprise an objective, wherein the stereo basis is determined by the distance between the two objectives perpendicular to the direction of view. The two half images are displayed to an observer in such a way that the observer obtains a spatial impression of the object field. To this end, a screen, for example, with a changing polarization may be provided in a manner known per se, with the observer wearing polarization spectacles with different polarizations of the two lenses.
However, the problem arising here in the case of a generic device for recording an image of an object field on a human or animal body is that the image generated on an electronic image recorder, and therefore also the image of the operation field displayed on a screen, rotates when the shaft rotates about an axis approximately parallel to the direction of view of the optical system. When use is made of a stereo optical system, the baseline of the stereoscopic optical system additionally rotates; therefore, the stereo basis is no longer displayed horizontally on the screen, and so the stereo effect, and hence also the spatial impression, may be lost. As a result, the orientation in the operation field is made more difficult, or even impossible, for a surgeon observing the screen.
JP 10192233 A has disclosed a stereoscopic electronic endoscope comprising an oblique view optical system, wherein provision is made for a motor-driven adjustment of a rotation element, which supports an optical system comprising two objective lens systems which are spaced apart transversely in relation to the optical axis, and two CCD image recorders assigned thereto. U.S. Pat. No. 5,689,365 has disclosed a stereoscopic endoscope, which comprises a front optical system with a single optical axis and a rear optical system with a plurality of optical axes. Together with two photoelectric image recorders, the rear optical system can be rotated about an axis parallel to the shaft of the endoscope relative to the front optical system.